'86 4kcs (not quattro) oil pressure light

[Luis Marques <marques@rtis.ray.com>]

I'm posting this for a friend of mine in Atlanta that recently bought a
4-cyl. 4kcs and has had a lot of little things to fix (including
swapping in a new used tranny).  I have been helping him, but need some
input from the folks with 4-cyl cars.

The oil pressure light and buzzer are going off whenever the car is hot
and the RPM's are above 2000 and it's driving him crazy.  We know the
car has oil pressure since it also has an oil pressure gauge.  My
immediate guess was that the high pressure switch was bad on the
dual-switch setup.  However, we are not sure where this switch is. 
There is a sensor screwed in on the back of the head (facing the
firewall) that has a single male terminal, but no wires are attached to
it.

Also, there is a fuel-injection-type two-terminal connector (with the
little wire that you have to press to remove it) around the back of the
head that is not connected to anything.  If I remember correctly, the
wires are Green/Yellow, and Brown/Black.  The question is whether the
sensor that's in place on the back of the head is actually the high
pressure switch, or if it was replaced with an older substitute that the
wiring harness can't plug into?  Any inputs are greatly appreciated.

TIA

Luis Marques
'87 4kcsq